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Linux Essentials 4.3
Where is the Data Stored?
63
Computer Science
Professional
04/20/2020

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Term
4.3 - What is the hierarchy in which binaries are stored?
Definition
"/" = Programs that are necessary in single-user mode
"/usr" = Most programs that are
Term
4.3 - What does /sbin contain?
Definition
Essential binaries for system administration
(Remember that some distros use symbolic links to point to /usr/sbin)
Term
4.3 - What does /bin contain?
Definition
Essential binaries for all users
(Remember that some distros use symbolic links to point to /usr/bin)
Term
4.3 - What does /usr/bin contain?
Definition
Includes most executable files
Term
4.3 - What does /usr/sbin contain?
Definition
Stores binaries for most systems administration
Term
4.3 - What does /usr/local/sbin contain?
Definition
Locally installed programs not managed by the package manager
Term
4.3 - Where is potential location in a users home directory for programs?
Definition
/home/$USER/bin
/home/$USER/.local/bin
Term
4.3 - What is the /etc directory used for?
Definition
System-wide configuration files (unlike user configurations which are stored in the user's home directory)
Term
4.3 - What is the "group" file in /etc used for?
Definition
System group database
Term
4.3 - What is the "hostname" file in /etc used for?
Definition
Contains the name of the host computer
Term
4.3 - What is the "profile" file in /etc used for?
Definition
System-wide configuration for Bash
Term
4.3 - What is the "hosts" file in /etc used for?
Definition
Contains a list of IP addresses and hostnames
Term
4.3 - What is the "passwd" file in /etc used for?
Definition
Contains a system user database comprised of seven colon separated fields.
Term
4.3 - What is the "shadow" file in /etc used for?
Definition
Contains the one-way hash values of users passwords
Term
4.3 - What does the initialization file known as "bash.bashrc" contain?
Definition
System-wide .bashrc file for interactive Bash shells (remember files with the "rc" characters are initialization files)
Term
4.3 - What does the "resolv.conf" file contain?
Definition
DNS configuration settings for the local resolver
Term
4.3 - What does the "sysctl.conf" file in /etc do?
Definition
A configuration file for setting system variables for the kernel.
Term
4.3 - What does the ".d" mean at the end of a file?
Definition
It means it is a directory.
Term
4.3 - What is the "." in ".file" mean?
Definition
The "." means the file is hidden
Term
4.3 - What is the ".bash_history" used for?
Definition
Stores the command line command history in the buffer.
Term
4.3 - What is the ".bash_logout" used for.
Definition
This file includes commands to execute when leaving the login shell
Term
4.3 - What is the ".bashrc" file used for?
Definition
This is a Bash initialization script for non-login bash-specific shells
Term
4.3 - What is the ".profile" file used for?
Definition
Bash initialization script for login shells read by many shells (not just Bash)
Term
4.3 - What is the PID for "systemd"
Definition
PID 1
Term
4.3 - What is the "config_4.9.0-9-amd64" file used for?
Definition
Config settings for the kernel such as options and modules that were compiled along with the kernel
Term
4.3 - What is the "initrd.img-4.9.0-9-amd64" file used for?
Definition
Initial RAM disk image that helps in the startup process by loading a temp root file system into memory
Term
4.3 - What is the "System-map-4.9.0-9-amd64" contain?
Definition
Device maps of the hard drives and this file manages memory prior to the loading of the kernel
Term
4.3 - What does the "vmlinuz-4.9.0-9-amd64" file contain?
Definition
This file is the kernel proper, stores in a self-extracting, space saving, compressed format
Term
4.3 - What is in the "grub" directory?
Definition
The Grub 2 bootloader
Term
4.3 - What is the "/proc" directory?
Definition
A pseudo file system, as it is not written to disk but stored completely in memory. It is dynamically populated every time the computer boots up and constantly reflects the current state of the system
Term
4.3 - Name three types of information we can get using "/proc"
Definition
1 - Running processes
2 - Kernel configuration
3 - System Hardware
Term
4.3 - What command can be used to find information about the processor?
Definition
cat /proc/cpuinfo
Term
4.3 - What is the command to find information about strings passed to the kernel
Definition
cat /proc/cmdline
Term
4.3 - How can you display a list of the modules loaded into the kernel?
Definition
cat /proc/modules
Term
What is the "/proc/sys" directory used for?
Definition
This directory includes kernel configuration settings in files divided into 8 subcategories.
Term
4.3 - What are the subcategories of the "/proc/sys" directory?
Definition
abi, debug, dev, fs, kernel, net, user, vm (remember that each one of these subdirectories act like switches containing a "0 or 1"
Term
4.3 - What is the /dev directory contain?
Definition
Device files for all connected devices, this is the interface between the devices and files using them
Term
4.3 - What are the two device categories?
Definition
Block and Character
Term
4.3 - What is a block device found in /dev?
Definition
These are devices in which data is written and read in blocks which can be individually addressed
Term
4.3 - What is a character device found in /dev?
Definition
These are devices in which data is written and read sequentially one character at a time
Term
4.3 - Name some examples of block devices.
Definition
Hard disks, flash drives, CD/DVD drives, SDCards
Term
4.3 - Name some examples of character devices.
Definition
Keyboards, text console, serial ports
Term
4.3 - What is "/dev/zero" used for?
Definition
Provides any null characters as requested
Term
4.3 - What is "/dev/null" used for?
Definition
Aka "bit bucket" will discard all information sent to it.
Term
4.3 - What is "/dev/urandom" used for?
Definition
Generates pseudo-random numbers
Term
4.3 - What is the "/sys" directory used for?
Definition
Contains information about hardware devices contained in "/dev" that the kernel references. This is were the "sysfs" is mounted.
Term
4.3 - What is the command to view current memory utilization?
Definition
"free"
Term
4.3 - Where does the command "free" parse its data from?
Definition
/proc/meminfo
Term
4.3 - What does the "free -b" switch do?
Definition
Displays memory utilization in byte format
Term
4.3 - What does the "free -m" switch do?
Definition
Displays memory utilization in megabyte format
Term
4.3 - What does the "free -g" switch do?
Definition
Displays memory utilization in gigabyte format
Term
4.3 - What are the letters that can modify the behavior of "top"?
Definition
M,N,T,P,R
Term
4.3 - What is way to view the process hierarchy?
Definition
pstree
Term
4.3 - How can you view static process information about the current shell?
Definition
ps
(with the -v switch, you can get verbose output)
(with the "uf" switches you can display the parent/child process relationship)
Term
4.3 - How can you display the current system load?
Definition
"uptime"
Term
4.3 - What do the last three fields in the output of the "uptime" command display?
Definition
1st = load average for the last minute
2nd = load average for the last 5 minutes
3rd = load average for the last 15 minutes
Term
4.3 - Where are logs sent when the kernel and processes start executing as well as the syslog daemon?
Definition
/var/log
Term
4.3 - What is the "/var/log/auth.log" file contain?
Definition
Stores information about authentication
Term
What does the "var/log/kern.log" files contain?
Definition
Stores kernel information
Term
4.3 - What is the "/var/log/syslog" file contain?
Definition
Stores system information
Term
4.3 - What is the "/var/log/message" file contain?
Definition
Stores system and application data
Term
4.3 - How can you view system and applications logs, one screen at a time?
Definition
sudo /var/log/messages | less
Term
4.3 - What do
"/var/log/wtmp" and "/var/log/btmp" files contain?
Definition
Non-plaintext logs that can be viewed with the "last" command
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